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Seeing through the Smoke: A Cannabis Specialist Untangles the Truth about Marijuana
Depending on which doctor you speak with, or which websites you read, cannabis could be an appealing, low-risk medicine – even an aid to wellness – or an insidiously addictive drug rotting the brains of our youth. This dissonance confuses young people, distressed patients, and paralyzes politicians, all while inviting dubious sources of information and resulting in uninformed choices, enhanced polarization, and a fragmented national policy. Seeing Through the Smoke is an unflinching examination at the grossly misunderstood drug that uses data-driven medical science and a critical historical perspective to reveal the truth behind cannabis. In this balanced and measured investigation, Cannabis specialist and Instructor in Medicine at Harvard Medical School Dr. Peter Grinspoon untangles the reality behind cannabis, revealing how we ended up with radically divergent understandings of the drug and pointing a way toward a middle ground that we can all share. Moving through an illuminating tour of the social history and the medical science behind cannabis, Grinspoon unpacks the layers of disinformation left by a sordid history of government propaganda, racial suppression, and indifference from the medical community to answer questions By focusing on the most critical purported harms—driving, pregnancy, addictiveness, memory—and by focusing on the most commonly cited medical benefits—relieving chronic pain, sleep, anxiety, PTSD, autism, and cancer—Seeing Through the Smoke will help patients, parents, doctors, health experts, regulators, and politicians move beyond biased perceptions and arrive at a shared reality towards cannabis.
442 pages, Hardcover
Published April 20, 2023
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Displaying 1 - 6 of 6 reviews
June 16, 2023
This is a such a comprehensive, thoughtful, objective look on cannabis in today’s world. It is very evident that Dr. Grinspoon not only took so much care in researching for this book but also made sure that he remained as unbiased as he could be, which is hard considering his own personal history with medical marijuana specifically. Not only is the book well developed, it’s also a pretty fun read compared to other books you would find in this genre. You really get to see the personality of Dr. Grinspoon come through at certain parts. There were even times when I chuckled out loud! I could not recommend this book more for anyone, no matter where you stand on legalization. Reading this book made me hopeful for the future of the medical field when it comes to cannabis.
October 23, 2025
Alas, I missed the chance to make Peter Grinspoon's Seeing Through the Smoke the 420th book that I've ever read. Still, it's fairly close to sitting in that position.
Since, in what follows, I will devote more time to criticizing this book than to praising it, allow me to immediately and comprehensively dispel all possible misunderstandings by stating at the very outset that it is, on the whole, really quite a good piece of work. For those who are almost totally ignorant of the scientific literature surrounding marijuana and its various medicinal consequences, as I was, it can serve as a simple and accessible introduction to an enormous and expanding field. Though Grinspoon makes no effort to conceal his conviction that marijuana and other illicit drugs should be available to all adults for whatever medicinal or recreational purposes they deem to be appropriate — a forthrightness for which, in my view, he deserves praise — he makes a sincere effort to be evenhanded in his examination of the relevant issues, and his book has the special virtue of deftly avoiding the irrational fanaticism that is so often exhibited by each of the antagonists in most political conflicts. While he takes great pains to point out the rather obvious fact that the U.S. government's crusade against cannabis and other drugs, dating back to at least 1937, has introduced systemic distortions into all of the scientific research surrounding cannabis and, in many clear cases, has unsalvageably vitiated its results, he cautions against the perhaps understandable temptation on the part of some of the drug's most ardent boosters to impale themselves on the dogmas of their own side.
Indisputable though it may be that the U.S. government has, for decades, deprived researchers who were curious about investigating the potential benefits of cannabis of the funds necessary to conduct their inquiries; undeniable though it may be that a great many of the studies on the medicinal and psychoactive effects of cannabis performed under these tendentious auspices have been riddled with rather obvious methodological holes — lacking proper controls, conflating correlation with causation, and often passing over the urgent need for longitudinal evidence in complete silence; and unquestionable though it may be that the dearth of randomized controlled trials demonstrating cannabis' benefits — which, as Grinspoon repeatedly underlines, is an unfortunate situation that only exists because of prohibition — has been used as an excuse by law enforcement, political advocacy groups, and even the medical profession to ignore other kinds of evidence that cannabis does help people and can effectively treat at least some conditions — it does not follow that cannabis' advocates are justified in shutting their eyes to all evidence of its harms and proclaiming it a miraculous wonder drug that can accomplish seemingly anything.
In chapters devoted to each of the following issues — psychosis and schizophrenia; addiction; pregnancy and breastfeeding; driving while high; and the respective effects of marijuana on the cognitive functioning, emotional well-being, and brain morphologies of both adults and teens — Grinspoon provides nuanced, balanced, and fair discussions. When robust indications of harm exist, or when the evidence is ambiguous — as in the cases of pregnant women, drivers, and teens — he counsels caution and advocates not using the drug. At the same time, he gleefully savages the embarrassing methodological shoddiness of many of our purported "scientific experts" on cannabis. There is, for example, absolutely no reason to think that using marijuana causes schizophrenia or any sort of long-lasting psychotic episodes. Rather shamefully, the studies purporting to "prove" this connection do not control for any genetic predispositions to these conditions. When the controls are introduced, the link disappears. To my genuine surprise, Grinspoon's book also showed me that there is no evidence that responsible recreational drug use causes brain abnormalities in otherwise healthy adults. The studies purporting to show this are all cross-sectional rather than longitudinal — that is, they only show images of the brains of drug users at certain discrete moments rather than displaying these morphological changes over time. That means that we cannot rule out the possibility that such changes as have been observed would not have occurred naturally, even in the absence of drug use.
(As a brief aside, despite Grinspoon's criticisms of the medical community's historic attitudes toward cannabis, he remains fairly naive about the problems that plague science in general. Studies like this rather extraordinary one from John Bohannon — and there are many others that I could have cited — paint a dismal and pitiful picture. In his study, Bohannon decided to run a sting against a scientific journal. He submitted an article to the journal that contained a number of deliberately and strategically placed errors, with the aim of determining how many of these errors would be detected during peer review. To express matters with the utmost gentility, the results were not encouraging. Insofar as it is used as a cudgel to silence those with heterodox views on various scientific subjects, there is ample reason to question the very seriousness of the peer review process. In true science, mere authority is meaningless, and only the strength of one's argumentation can carry weight.)
Grinspoon also writes a series of interesting chapters on how cannabis has been shown to help many people with opioid addition, insomnia, autism, anxiety and depression. He has another chapter in which his discusses the ability of some cannabinoids to destroy cancer cells under laboratory conditions, but he admits that the evidence base for this is not robust enough to inform any definitive treatments. Another general chapter on the human endocannabinoid system — a series of special neural receptors located all over the human body that seem naturally adapted to absorb some of the special compounds in cannabis — provides an interesting discussion of the mechanisms that may enable cannabis to assist people with these ailments.
Since this all sounds quite fascinating, and Grinspoon's overview of the literature is both sweeping and balanced, what could I have to object to in this book? There are a few things.
First, Grinspoon repeats the tired old canard that, while non-whites use cannabis at the same rates that white people do, they are arrested in vastly disproportionate numbers. There is simply no reliable evidence that the first part of that statement is true. The evidence purporting to demonstrate it consists entirely of surveys. Researchers simply ask people of various races whether they have used cannabis (or other drugs) over a given interval of time, collect their answers, and do not question them. In the few cases where researchers have taken the trouble to test repondents after asking about their drug use, the results have almost always shown that non-whites were many times more likely than whites to lie. This study from 2005 and this one from 2008, among others, show exactly this.
Note that it does not matter whether one believes that non-whites have good reasons to lie about their drug use; the point is only that they are more likely to lie about it than whites are. Of course, I am entirely in agreement with Grinspoon that anti-drug laws are flagrantly unjust, monstrously immoral, and unable to ultimately achieve the purpose for which they were ostensibly created. My point is only that, when controlling for the actual, rather than the self-declared, rates of drug use among the various races, there is no evidence that the drug war has disproportionately impacted non-white communities.
I must call attention to something else: When discussing a series of poorly designed, invidiously interpreted and often utterly contradictory studies by Dr. Madeline Meir, which purport to examine the causal relationships between cannabis consumption and IQ levels, Grinspoon makes the following whopper of a statement on pp. 215-216:
For anyone who is even marginally familiar with either statistics or IQ testing, this is a lamentable farrago of conceptual confusions. To begin with, assuming an average IQ of 100 and a standard deviation of 15 points — the former of which is defined as the average of the white population (members of other races are scored relative to this parameter, as all IQ scores are ultimately only relative measurements), and the latter of which is standard practice, given how the tests are normed — it follows that approximately 68% of the population has an IQ of between 85 and 115. Something which applies to 68% of a population is only average in the rather unusual circumstance in which 68% of all values in the distribution just so happen to be the mean value — a state of affairs which decidedly does not hold in the case of IQ, which, as everyone who has investigated the subject knows, is normally distributed. Grinspoon either doesn't understand what a standard deviation is, doesn't understand what an average is, or is afflicted by some as-yet-unfathomed species of muddleheadedness which the present writer cannot be reasonably expected to divine. It is entirely accurate to describe an IQ of 93.8 as "below average"; indeed, such a statement is true by definition.
Of course, the methodological objections that Grinspoon raises to that part of Meier's work which he discusses are perfectly sound. Her studies do not control for the presence of other drugs, like alcohol or tobacco, which may also adversely affect IQ and brain structure or cognitive functioning; they are not longitudinal, which means that we cannot conclude that any observed structural changes in the brains of cannabis users would not have occurred naturally and in the absence of cannabis use; and lastly, they are merely correlational and, in truth, say nothing about the causal relation in which cannabis use and observed cognitive declines stand.
It is especially unfortunate, however, that in his comments on IQ testing, Grinspoon failed to remember the last of these points. IQ is indeed "sensitive" to poverty, but is this because poverty causes low IQ scores or because having a low IQ score makes it more likely that one will be poor? Grinspoon is evidently so sure that he knows the answer to this question that he does not even stop to reflect upon the fact that he might confusing correlation and causation in precisely the same way that the harm-focused cannabis researchers whom he so rightly upbraids do. In fact, the vast bulk of the existing evidence on the matter suggests that it is low IQ which causes poverty, and not vice versa. Although IQ does correlate with socioeconomic status, it also strongly correlates with things that cannot be plausibly explained by environmental factors, like the cortical thickness of one's brain.
This is not the place to provide an overview of the filed of intelligence research, but suffice it to say that Grinspoon's comments are totally uncomprehending. Though he certainly deserves plaudits for his efforts to expose the ignorant nonsense that so many believe about cannabis, it does not help his case to spread equally obtuse balderdash about IQ tests. Those who are interested in this subject may want to consult books like Richard Haier's The Neuroscience of Intelligence, Russell Warne's In the Know: Debunking 35 Myths about Human Intelligence, and Earl Hunt's Human Intelligence.
Finally, there remain some admittedly minor gripes to address. I found Grispoon's repeated misuse of the phrase "begs the question" to be slightly irksome. He misapplies this phrase, as nearly everyone does, by using it when he really means to say "raises the question." To "beg the question" is to assume that something is true without arguing for it. While ordinarily, I would not consider such a faux pas to be worth mentioning, Grinspoon, for reasons that are utterly mysterious to me, finds it necessary to repeatedly inform his readers that he had taken philosophy classes while in college. Was the meaning of begging the question never discussed in these classes? Perhaps Grinspoon was high during that particular lecture.
Throughout the book, Grinspoon also feels the need to share with his readers his utterly unsolicited political opinions. Perhaps some will find these asides charming — it is abundantly clear that the good doctor imagines himself to be quite clever for making them — but to me, they add nothing.
My objections aside, however, I want to insist again that Grinspoon's is a valuable book. Every society must decide for itself how best to strike a balance between internal and external controls upon its members' behavior; the more internal controls there are, the fewer external controls are necessary, and vice versa. The ultimate reason why adults should be allowed to consume cannabis and other recreational drugs at their leisure is that, if a populace cannot be trusted to behave responsibly with potentially dangerous substances, then it ultimately cannot be trusted to maintain any of its liberties. If the paternalistic argument is truly correct that people cannot summon up the self-control necessary to eschew using drugs to excess, then it is difficult to imagine why they should be allowed to vote. A government which insists on treating its people like a gaggle of helpless children and miserable slaves will, soon enough, transform them into precisely that, and a people who acquiesces in such treatment will only aid in the transformation. We all owe a debt of gratitude to Peter Grinspoon for doing something to help us avoid that appalling fate.
Since, in what follows, I will devote more time to criticizing this book than to praising it, allow me to immediately and comprehensively dispel all possible misunderstandings by stating at the very outset that it is, on the whole, really quite a good piece of work. For those who are almost totally ignorant of the scientific literature surrounding marijuana and its various medicinal consequences, as I was, it can serve as a simple and accessible introduction to an enormous and expanding field. Though Grinspoon makes no effort to conceal his conviction that marijuana and other illicit drugs should be available to all adults for whatever medicinal or recreational purposes they deem to be appropriate — a forthrightness for which, in my view, he deserves praise — he makes a sincere effort to be evenhanded in his examination of the relevant issues, and his book has the special virtue of deftly avoiding the irrational fanaticism that is so often exhibited by each of the antagonists in most political conflicts. While he takes great pains to point out the rather obvious fact that the U.S. government's crusade against cannabis and other drugs, dating back to at least 1937, has introduced systemic distortions into all of the scientific research surrounding cannabis and, in many clear cases, has unsalvageably vitiated its results, he cautions against the perhaps understandable temptation on the part of some of the drug's most ardent boosters to impale themselves on the dogmas of their own side.
Indisputable though it may be that the U.S. government has, for decades, deprived researchers who were curious about investigating the potential benefits of cannabis of the funds necessary to conduct their inquiries; undeniable though it may be that a great many of the studies on the medicinal and psychoactive effects of cannabis performed under these tendentious auspices have been riddled with rather obvious methodological holes — lacking proper controls, conflating correlation with causation, and often passing over the urgent need for longitudinal evidence in complete silence; and unquestionable though it may be that the dearth of randomized controlled trials demonstrating cannabis' benefits — which, as Grinspoon repeatedly underlines, is an unfortunate situation that only exists because of prohibition — has been used as an excuse by law enforcement, political advocacy groups, and even the medical profession to ignore other kinds of evidence that cannabis does help people and can effectively treat at least some conditions — it does not follow that cannabis' advocates are justified in shutting their eyes to all evidence of its harms and proclaiming it a miraculous wonder drug that can accomplish seemingly anything.
In chapters devoted to each of the following issues — psychosis and schizophrenia; addiction; pregnancy and breastfeeding; driving while high; and the respective effects of marijuana on the cognitive functioning, emotional well-being, and brain morphologies of both adults and teens — Grinspoon provides nuanced, balanced, and fair discussions. When robust indications of harm exist, or when the evidence is ambiguous — as in the cases of pregnant women, drivers, and teens — he counsels caution and advocates not using the drug. At the same time, he gleefully savages the embarrassing methodological shoddiness of many of our purported "scientific experts" on cannabis. There is, for example, absolutely no reason to think that using marijuana causes schizophrenia or any sort of long-lasting psychotic episodes. Rather shamefully, the studies purporting to "prove" this connection do not control for any genetic predispositions to these conditions. When the controls are introduced, the link disappears. To my genuine surprise, Grinspoon's book also showed me that there is no evidence that responsible recreational drug use causes brain abnormalities in otherwise healthy adults. The studies purporting to show this are all cross-sectional rather than longitudinal — that is, they only show images of the brains of drug users at certain discrete moments rather than displaying these morphological changes over time. That means that we cannot rule out the possibility that such changes as have been observed would not have occurred naturally, even in the absence of drug use.
(As a brief aside, despite Grinspoon's criticisms of the medical community's historic attitudes toward cannabis, he remains fairly naive about the problems that plague science in general. Studies like this rather extraordinary one from John Bohannon — and there are many others that I could have cited — paint a dismal and pitiful picture. In his study, Bohannon decided to run a sting against a scientific journal. He submitted an article to the journal that contained a number of deliberately and strategically placed errors, with the aim of determining how many of these errors would be detected during peer review. To express matters with the utmost gentility, the results were not encouraging. Insofar as it is used as a cudgel to silence those with heterodox views on various scientific subjects, there is ample reason to question the very seriousness of the peer review process. In true science, mere authority is meaningless, and only the strength of one's argumentation can carry weight.)
Grinspoon also writes a series of interesting chapters on how cannabis has been shown to help many people with opioid addition, insomnia, autism, anxiety and depression. He has another chapter in which his discusses the ability of some cannabinoids to destroy cancer cells under laboratory conditions, but he admits that the evidence base for this is not robust enough to inform any definitive treatments. Another general chapter on the human endocannabinoid system — a series of special neural receptors located all over the human body that seem naturally adapted to absorb some of the special compounds in cannabis — provides an interesting discussion of the mechanisms that may enable cannabis to assist people with these ailments.
Since this all sounds quite fascinating, and Grinspoon's overview of the literature is both sweeping and balanced, what could I have to object to in this book? There are a few things.
First, Grinspoon repeats the tired old canard that, while non-whites use cannabis at the same rates that white people do, they are arrested in vastly disproportionate numbers. There is simply no reliable evidence that the first part of that statement is true. The evidence purporting to demonstrate it consists entirely of surveys. Researchers simply ask people of various races whether they have used cannabis (or other drugs) over a given interval of time, collect their answers, and do not question them. In the few cases where researchers have taken the trouble to test repondents after asking about their drug use, the results have almost always shown that non-whites were many times more likely than whites to lie. This study from 2005 and this one from 2008, among others, show exactly this.
Note that it does not matter whether one believes that non-whites have good reasons to lie about their drug use; the point is only that they are more likely to lie about it than whites are. Of course, I am entirely in agreement with Grinspoon that anti-drug laws are flagrantly unjust, monstrously immoral, and unable to ultimately achieve the purpose for which they were ostensibly created. My point is only that, when controlling for the actual, rather than the self-declared, rates of drug use among the various races, there is no evidence that the drug war has disproportionately impacted non-white communities.
I must call attention to something else: When discussing a series of poorly designed, invidiously interpreted and often utterly contradictory studies by Dr. Madeline Meir, which purport to examine the causal relationships between cannabis consumption and IQ levels, Grinspoon makes the following whopper of a statement on pp. 215-216:
There are also quite a lot of problems with IQ testing in general (i.e., it's not very accurate and is sensitive to many variables such as poverty). More specifically, when Meier says that these cannabis users have 'below-average IQ as adults' — the range for normal IQ is 85-115 (i.e., one standard deviation), and the purported drop she shows is to 93.8 (despite all of her methodological flaws) — this is not an accurate statement.
For anyone who is even marginally familiar with either statistics or IQ testing, this is a lamentable farrago of conceptual confusions. To begin with, assuming an average IQ of 100 and a standard deviation of 15 points — the former of which is defined as the average of the white population (members of other races are scored relative to this parameter, as all IQ scores are ultimately only relative measurements), and the latter of which is standard practice, given how the tests are normed — it follows that approximately 68% of the population has an IQ of between 85 and 115. Something which applies to 68% of a population is only average in the rather unusual circumstance in which 68% of all values in the distribution just so happen to be the mean value — a state of affairs which decidedly does not hold in the case of IQ, which, as everyone who has investigated the subject knows, is normally distributed. Grinspoon either doesn't understand what a standard deviation is, doesn't understand what an average is, or is afflicted by some as-yet-unfathomed species of muddleheadedness which the present writer cannot be reasonably expected to divine. It is entirely accurate to describe an IQ of 93.8 as "below average"; indeed, such a statement is true by definition.
Of course, the methodological objections that Grinspoon raises to that part of Meier's work which he discusses are perfectly sound. Her studies do not control for the presence of other drugs, like alcohol or tobacco, which may also adversely affect IQ and brain structure or cognitive functioning; they are not longitudinal, which means that we cannot conclude that any observed structural changes in the brains of cannabis users would not have occurred naturally and in the absence of cannabis use; and lastly, they are merely correlational and, in truth, say nothing about the causal relation in which cannabis use and observed cognitive declines stand.
It is especially unfortunate, however, that in his comments on IQ testing, Grinspoon failed to remember the last of these points. IQ is indeed "sensitive" to poverty, but is this because poverty causes low IQ scores or because having a low IQ score makes it more likely that one will be poor? Grinspoon is evidently so sure that he knows the answer to this question that he does not even stop to reflect upon the fact that he might confusing correlation and causation in precisely the same way that the harm-focused cannabis researchers whom he so rightly upbraids do. In fact, the vast bulk of the existing evidence on the matter suggests that it is low IQ which causes poverty, and not vice versa. Although IQ does correlate with socioeconomic status, it also strongly correlates with things that cannot be plausibly explained by environmental factors, like the cortical thickness of one's brain.
This is not the place to provide an overview of the filed of intelligence research, but suffice it to say that Grinspoon's comments are totally uncomprehending. Though he certainly deserves plaudits for his efforts to expose the ignorant nonsense that so many believe about cannabis, it does not help his case to spread equally obtuse balderdash about IQ tests. Those who are interested in this subject may want to consult books like Richard Haier's The Neuroscience of Intelligence, Russell Warne's In the Know: Debunking 35 Myths about Human Intelligence, and Earl Hunt's Human Intelligence.
Finally, there remain some admittedly minor gripes to address. I found Grispoon's repeated misuse of the phrase "begs the question" to be slightly irksome. He misapplies this phrase, as nearly everyone does, by using it when he really means to say "raises the question." To "beg the question" is to assume that something is true without arguing for it. While ordinarily, I would not consider such a faux pas to be worth mentioning, Grinspoon, for reasons that are utterly mysterious to me, finds it necessary to repeatedly inform his readers that he had taken philosophy classes while in college. Was the meaning of begging the question never discussed in these classes? Perhaps Grinspoon was high during that particular lecture.
Throughout the book, Grinspoon also feels the need to share with his readers his utterly unsolicited political opinions. Perhaps some will find these asides charming — it is abundantly clear that the good doctor imagines himself to be quite clever for making them — but to me, they add nothing.
My objections aside, however, I want to insist again that Grinspoon's is a valuable book. Every society must decide for itself how best to strike a balance between internal and external controls upon its members' behavior; the more internal controls there are, the fewer external controls are necessary, and vice versa. The ultimate reason why adults should be allowed to consume cannabis and other recreational drugs at their leisure is that, if a populace cannot be trusted to behave responsibly with potentially dangerous substances, then it ultimately cannot be trusted to maintain any of its liberties. If the paternalistic argument is truly correct that people cannot summon up the self-control necessary to eschew using drugs to excess, then it is difficult to imagine why they should be allowed to vote. A government which insists on treating its people like a gaggle of helpless children and miserable slaves will, soon enough, transform them into precisely that, and a people who acquiesces in such treatment will only aid in the transformation. We all owe a debt of gratitude to Peter Grinspoon for doing something to help us avoid that appalling fate.
July 9, 2025
What a waste of time! If you are looking at things like safety of using the legal products, and actual info on what is dangerous and what isn't, you won't find it here. You will instead find out how the laws are all essentially "out to get you". Keep looking for a source with better info. I did learn though that the author is a 30 year user of Cannabis and had an opioid addiction. Now he is just a heavy Cannabis using doctor. There has to be better info out there somewhere.
February 21, 2024
This book is a must read for anyone who wants to unbiasedly educate themselves on the history, benefits, and harms of marijuana. The author pulls on his real life experience as a doctor, a user, and the son of Lester Grinspoon, a pioneer in the marijuana legalization movement.
December 11, 2023
NetGalley ARC review
Interest read for anyone interested in this topic. Alittle dry but worth the read.
Interest read for anyone interested in this topic. Alittle dry but worth the read.
January 24, 2024
Informative and enlightening.
Displaying 1 - 6 of 6 reviews